Conventionally, a “security system” for detecting an intruder using a laser range finder that employs a laser beam as a light source has been proposed (for example, see Patent Literature 1).
This “security system” includes a sensor unit, a swivel camera unit, and a control unit. The sensor unit sets a monitoring area at a scan angle for two-dimensionally scanning a light of an optical range finder. When the sensor unit detects an intruder within the area, the sensor unit outputs distance data and angle data of the intruder. The swivel camera unit is installed on an electrically-operated swivel base, and turns in conjunction with the sensor unit. The control unit has a function of: detecting the presence of an intruder by continuously detecting change in the distance data or the angle data several times at the sensor unit; calculating the position of the intruder using the changed distance data and angle data from the sensor unit; turning the swivel camera unit on the electrically-operated swivel base in accordance with the positional data; and displaying image data of the intruder on a monitor.
An “object identifying method using an area sensor” has also been proposed (for example, see Patent Literature 2) although this method is slightly different from a crime prevention apparatus and a security system. This method can accurately identify a pedestrian or the like using a laser beam.
According to this “object identifying method using the area sensor”, an area sensor using a laser detector scans while projecting a pulse laser beam within a detection range that covers a walking area to which the pedestrian is guided and a peripheral area of the walking area, so as to measure a reflection time of the light. This method obtains the difference between a reflection time when an object is not present and a reflection time when an object is present for each scanning point to perform calculation of the shape and the size of the object and the vector based on positional change of the object for each scanning. Based on this operation signal, the method identifies an object that moves in the walking area along a guiding direction and an object that moves in a direction across the walking area.
Furthermore, in view of problems in these conventional techniques, the inventors of this application have already proposed a laser area sensor that does not only facilitate setting an appropriate security zone for preventing false detection as much as possible corresponding to the actual installation site, the security purpose, or the like, but also facilitates setting any security zone (see Patent Literature 3).
This “laser area sensor” includes a laser range finder, a scanning mechanism unit, a distance-information acquiring unit, a human-body determining unit, and a human body-detection signal output unit. The laser range finder uses a time after a laser beam emits before a reflected light returns from an object present in a direction of the emission so as to measure the distance to the object. The scanning mechanism unit changes the measurement direction of this laser range finder. The distance-information acquiring unit periodically performs measurement using the laser range finder while changing the measurement direction using this scanning mechanism unit, so as to form a detection area and to acquire distance information for each direction within the detection area in chronological order. The human-body determining unit extracts a portion estimated to correspond to a human body from the distance information acquired by this distance-information acquiring unit, and then determines whether or not the object is a human body based on a movement state of the extracted portion in chronological order. The human body-detection signal output unit outputs a human body detection signal in the case where this human-body determining unit determines that a human body is present.